Modeling of ionospheric scintillation at low-latitude

Patel, Kalpana D.; Subrahmanyam, P.; Singh, Ashutosh K.

doi:10.1016/j.asr.2010.09.017

Cited by 11 publications

(11 citation statements)

References 42 publications

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“…The raypaths through the GUVI electron density data cube indicate that the SATCOM signal passed through an electron density gradient declining from background electron density of approximately 8 × 10 5 cm −3 to depleted electron density of 2 × 10 5 cm −3 . With that background electron density and a ∆ N / N of 0.75, we estimate that ionospheric anomalies could have generated SATCOM (UHF 250 MHz) scintillation at the level S4 = 0.3 (standard deviation of intensity divided by mean), corresponding to maximum fade depths of 3.6 dB for direct ray D [ Patel et al ., ]. When considering the combined effect of scintillation with destructive interference and of reflected rays coming off the terrain with reflectivity estimated to be 0.7 (or more) for medium dry ground and grazing angles less than 10°, we estimate maximum fade depths greater than 40 dB, which would cause an outage.…”

Section: Combined Scintillation and Multipath Effectsmentioning

confidence: 98%

Progress toward forecasting of space weather effects on UHF SATCOM after Operation Anaconda

et al. 2014

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Space weather impacts on communications are often presented as a raison d'etre for studying space weather (e.g., Solar and Space Physics: A Science for a Technological Society, 2013). Here we consider a communications outage during Operation Anaconda in Afghanistan that may have been related to ionospheric disturbances. Early military operations occurred during the peak of solar cycle 23 when ionospheric variability was enhanced. During Operation Anaconda, the Battle of Takur Ghar occurred at the summit of a 3191 m Afghan mountaintop on 4 March 2002 when the ionosphere was disturbed and could have affected UHF Satellite Communications (SATCOM). In this paper, we consider UHF SATCOM outages that occurred during repeated attempts to notify a Quick Reaction Force (QRF) on board an MH-47H Chinook to avoid a "hot" landing zone at the top of Takur Ghar. During a subsequent analysis of Operation Anaconda, these outages were attributed to poor performance of the UHF radios on the helicopters and to blockage by terrain. However, it is also possible that ionospheric anomalies together with multipath effects could have combined to decrease the signal-to-noise ratio of the communication links used by the QRF. A forensics study of Takur Ghar with data from the Global Ultraviolet Imager on the NASA Thermosphere Ionosphere Mesosphere Energetics and Dynamics mission showed the presence of ionospheric bubbles (regions of depleted electron density) along the line of sight between the Chinook and the UHF communications satellites in geostationary orbit that could have impacted communications. The events of 4 March 2002 motivated us to develop the Mesoscale Ionospheric Simulation Testbed model, which can be used to improve warnings of potential UHF outages during future military operations.

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Section: Combined Scintillation and Multipath Effectsmentioning

confidence: 98%

Progress toward forecasting of space weather effects on UHF SATCOM after Operation Anaconda

et al. 2014

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“…The raypaths through the GUVI electron density data cube indicate that the SATCOM signal passed through an electron density gradient declining from background electron density of approximately 8 × 10 5 cm À3 to depleted electron density of 2 × 10 5 cm À3 . With that background electron density and a ΔN/N of 0.75, we estimate that ionospheric anomalies could have generated SATCOM (UHF 250 MHz) scintillation at the level S4 = 0.3 (standard deviation of intensity divided by mean), corresponding to maximum fade depths of 3.6 dB for direct ray D [Patel et al, 2011]. When considering the combined effect of scintillation with destructive interference and of reflected rays coming off the terrain with reflectivity estimated to be 0.7 (or more) for medium dry ground and grazing angles less than 10°, we estimate maximum fade depths greater than 40 dB, which would cause an outage.…”

Section: Combined Scintillation and Multipath Effectsmentioning

confidence: 99%

Space Weather Quarterly Volume 11, Issue 4, 2014

2014

Space Weather Quarterly

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“…is the turbulence strength (Rumsey 1975), the Fresnel zone parameter Z = Z R sec θ/4π , Z R = zz s /z + z s , z is the distance to the phase screen, z s is the distance to the GPS satellite, r e = 2.8 × 10 −15 m is the classical electron radius, θ is the zenith angle of the signal path, and L is the irregular layer thickness. We have assumed L = 200 km (Basu et al 1976;Patel et al 2011). is the wavelength at GPS L1 frequency, q o = 2π/L o is the outer-scale cut-off number, L o is the outer scale of the irregularity, N 2 e is the variance of N e at the satellite location and the angle brackets denote ensemble averaging.…”

Section: Amplitude Scintillation From the Phase Screen Modelmentioning

confidence: 99%

“…A detailed derivation of the modeled S4 in Eq. 1 can be found in Patel et al (2011) and references therein.…”

Section: Amplitude Scintillation From the Phase Screen Modelmentioning

confidence: 99%

“…Furthermore, to overcome the limited spatial coverage of ground-based receivers, efforts have been made to derive scintillation for prediction/monitoring purposes from in situ electron density measurements as an alternative. One approach involves the derivation of scintillation from in situ electron density measurements using the weak phase screen model (Basu et al 1976;Rino 1979;Crane 1977;Wernik et al 2007;Patel et al 2011;Liu et al 2012;Alfonsi et al 2017). To test the ionospheric scintillation model, coincident observations of electron density in the ionosphere and scintillation signals on the ground is necessary (Liu et al 2012).…”

Section: Introductionmentioning

confidence: 99%

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Ionospheric irregularities and scintillations: a direct comparison of in situ density observations with ground-based L-band receivers

Aol

Buchert

Jurua

2020

Earth Planets Space

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Ionospheric irregularities can affect satellite communication and navigation by causing scintillations of radio signals. The scintillations are routinely measured using ground-based networks of receivers. This study presents observations of ionospheric irregularities by Langmuir probes on the Swarm satellites. They are compared with amplitude scintillation events recorded by the Global Positioning System-Scintillation Network and Decision Aid (GPS-SCINDA) receiver installed in Mbarara (Lat: $$0.6^{\circ }\hbox {S}$$ 0 . 6 ∘ S , Lon: $$30.8^{\circ }\hbox {E}$$ 30 . 8 ∘ E , Mag. lat: $$10.2^{\circ }\hbox {S}$$ 10 . 2 ∘ S ). The study covers the years from 2014 to 2018 when both data sets were available. It was found that the ground-based amplitude scintillations were enhanced when Swarm registered ionospheric irregularities for a large number of passes. The number of matching observations was greater for Swarm A and C which orbited at lower altitudes compared to Swarm B. However, some counterexamples, i.e., cases when in situ electron density fluctuations were not associated with any observed L-band amplitude scintillation and vice versa, were also found. Therefore, mismatches between observed irregularity structures and scintillations can occur just over a few minutes and within distances of a few tens of kilometers. The amplitude scintillation strength, characterized by the S4 index was estimated from the electron density data using the well-known phase screen model for weak scattering. The derived amplitude scintillation was on average lower for Swarm B than for A and C and less in accordance with the observed range. Irregularities at an altitude of about 450 km contribute strongly to scintillations in the L-band, while irregularities at about 510-km altitude contribute significantly less. We infer that in situ density fluctuations observed on passes over or near Mbarara may be used to indicate the risk that ionospheric radio wave scintillations occur at that site.

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Modeling of ionospheric scintillation at low-latitude

Cited by 11 publications

References 42 publications

Progress toward forecasting of space weather effects on UHF SATCOM after Operation Anaconda

Progress toward forecasting of space weather effects on UHF SATCOM after Operation Anaconda

Space Weather Quarterly Volume 11, Issue 4, 2014

Ionospheric irregularities and scintillations: a direct comparison of in situ density observations with ground-based L-band receivers

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